A petard was a small bomb used to blow up gates and walls when breaching fortifications, which dates back to the 16th century. (Wikipedia)

[At last I know what the Shakespearean phrase “hoist with his own petard” means! If a petard detonated prematurely, the petardier would be lifted, or hoisted, by the explosion. In other words, the bomber would be blown up by his own bomb.]